The present invention relates to methods and devices for reducing the volume of a body lumen or cavity and, in particular, for reducing the volume of a portion of the heart.
Embolic stroke is the nation""s third leading killer for adults, and is a major cause of disability. There are over 700,000 strokes per year in the United States alone. Of these, roughly 100,000 are hemoragic, and 600,000 are ischemic (either due to vessel narrowing or to embolism). The most common cause of embolic stroke emanating from the heart is thrombus formation due to atrial fibrillation. Approximately 80,000 strokes per year are attributable to atrial fibrillation. Atrial fibrillation is an arrhythmia of the heart that results in a rapid and chaotic heartbeat that produces lower cardiac output and irregular and turbulent blood flow in the vascular system. There are over five million people worldwide with atrial fibrillation, with about four hundred thousand new cases reported each year. Atrial fibrillation is associated with a 500 percent greater risk of stroke due to the condition. A patient with atrial fibrillation typically has a significantly decreased quality of life due, in part, to the fear of a stroke, and the pharmaceutical regimen necessary to reduce that risk.
For patients who develop atrial thrombus from atrial fibrillation, the clot normally occurs in the left atrial appendage (LAA) of the heart. The LAA is a cavity which looks like a small finger or windsock and which is connected to the lateral wall of the left atrium between the mitral valve and the root of the left pulmonary vein. The LAA normally contracts with the rest of the left atrium during a normal heart cycle, thus keeping blood from becoming stagnant therein, but often fails to contract with any vigor in patients experiencing atrial fibrillation due to the discoordinate electrical signals associated with AF. As a result, thrombus formation is predisposed to form in the stagnant blood within the LAA.
Blackshear and Odell have reported that of the 1288 patients with non-rheumatic atrial fibrillation involved in their study, 221 (17%) had thrombus detected in the left atrium of the heart. Blackshear J L, Odell J A., Appendage Obliteration to Reduce Stroke in Cardiac Surgical Patients With Atrial Fibrillation. Ann Thorac. Surg., 1996.61(2):755-9. Of the patients with atrial thrombus, 201 (91%) had the atrial thrombus located within the left atrial appendage. The foregoing suggests that the elimination or containment of thrombus formed within the LAA of patients with atrial fibrillation would significantly reduce the incidence of stroke in those patients.
Pharmacological therapies for stroke prevention such as oral or systemic administration of warfarin or the like have been inadequate due to serious side effects of the medications and lack of patient compliance in taking the medication. Invasive surgical or thorascopic techniques have been used to obliterate the LAA, however, many patients are not suitable candidates for such surgical procedures due to a comprised condition or having previously undergone cardiac surgery. In addition, the perceived risks of even a therascopic surgical procedure often outweigh the potential benefits. See Blackshear and Odell, above. See also Lindsay BD., Obliteration of the Left Atrial Appendage: A Concept Worth Testing, Ann Thorac. Surg., 1996.61(2):515.
Despite the various efforts in the prior art, there remains a need for a minimally invasive method and associated devices for reducing the risk of thrombus formation in the left atrial appendage. There also remains a need for a minimally invasive method for reducing the volume of hollow organs such as portions of the heart.
There is provided in accordance with one aspect of the present invention, a closure catheter for closing an opening in tissue, or reducing the volume of a body lumen, hollow organ or other body cavity. The catheter and methods of its use are useful in a variety of procedures, such as treating (closing) wounds and naturally or surgically created apertures or passageways. Applications include, but are not limited to, atrial septal defect closure, patent ductus arteriosis closure, aneurysm isolation and graft and/or bypass anostomosis procedures.
The closure catheter comprises an elongate, flexible catheter body, having a proximal end and a distal end, and a longitudinal axis extending therebetween. At least two anchor supports are provided on the distal end. The anchor supports are movable between a first position in which they are substantially parallel with the axis, and a second position in which they are inclined laterally from the axis. A control is provided on the proximal end for moving the anchor supports from the axial orientation into the inclined orientation.
Preferably, from about four anchor supports to about eight anchor supports are provided. At least one, and preferably all, of the anchor supports comprises a tube, having a tissue anchor movably positioned within the tube.
There is provided in accordance with another aspect of the present invention, a catheter for deploying at least one tissue anchor at an angle to the longitudinal axis of the catheter and into an adjacent tissue surface. The catheter comprises an elongate flexible body, having a proximal end and a distal end. At least one anchor support is provided on the body, and is movable between an axial orientation and an inclined orientation. A control is provided on the body for controlling movement of the anchor support between the axial orientation and the inclined orientation. At least one anchor is movably carried by the anchor support.
In one embodiment, the anchor support is biased towards the inclined orientation. The control comprises an axially movable actuator, for moving the anchor support between the axial orientation and the inclined orientation. The actuator comprises a core connected to the anchor support such that axial movement of the core advances the anchor support from the axial orientation to the inclined orientation.
In one embodiment, each anchor support removably carries an introducer which is removably connected to the anchor for driving the anchor into the tissue. The anchor comprises a tubular body, for sliceable receiving the introducer therethrough.
In accordance with a further aspect of the present invention, there is provided a method of securing a plurality of tissue anchors about the interior circumference of a tubular tissue structure. The method comprises the steps of providing a tissue anchor delivery catheter having a plurality of anchor supports movable between an axial orientation and an inclined orientation. An anchor is carried by each anchor support, each anchor having a suture secured thereto. The catheter is transluminally advanced to a target site within a tubular tissue structure while the anchor supports are in the axial orientation. The anchor supports are advanced from the axial orientation to the inclined orientation at a target site, and anchors are deployed from the anchor supports into the tissue.
In one embodiment, the advancing the anchor support step comprises axially moving a control on the catheter. Following securing the plurality of tissue anchors into the tissue, the method may additionally comprise the step of proximally retracting the sutures to draw the anchors radially inwardly towards each other to close the tubular tissue structure. In one application of the invention, the tubular tissue structure comprises the left atrial appendage.
In accordance with a further aspect of the present invention, there is provided a method of reducing the volume of the left atrial appendage. The method comprises the steps of providing a catheter having at least four tissue anchors thereon, the anchors each having a suture secured thereto. The catheter is advanced through the heart and into the left atrial appendage. The anchors are inclined radially outwardly from the axis of the catheter, towards the tissue surrounding the opening to the left atrial appendage. The anchors are deployed from the catheter and into the tissue, and the sutures are retracted to reduce the volume of the left atrial appendage.
Preferably, the inclining step comprises proximally retracting a control for inclining anchor supports which carry the anchors. In one embodiment, proximally retracting the control axially compresses the anchor support such that the anchors incline radially outwardly from the axis of the catheter.
In accordance with another aspect of the present invention, there is provided a method of reducing the volume of a portion of the heart. The method comprises the steps of providing a catheter having at least two and often four or more tissue anchors thereon, the anchors each having a suture secured thereto. The catheter is advanced into a portion of the heart, and the anchors are inclined radially outwardly from the axis of the catheter towards surrounding tissue. The anchors are deployed from the catheter into the tissue, and the sutures are retracted to reduce the volume of the portion of the heart. In one application, the portion of the heart comprises the left atrial appendage.
Further features and advantages of the present invention will become apparent to those of skill in the art in view of the detailed description of the preferred embodiment which follows, when considered together with the attached drawings and claims.